In wireless communications systems of the art, a variety of transmission protocols have been developed for providing airlink service to users. Exemplary network services based on such transmission protocols include High Rate Packet Data (HRPD), Long Term Evolution (LTE) and Universal Mobile Telecommunications System (UMTS). Each of these network services is defined in terms of a particular Radio Access Technology (RAT), and, in general, the RAT defining each different transmission protocol requires a unique RF configuration for transmission and reception of communications based on a given RAT.
Heterogeneous networks (HetNets) are now being developed wherein cells of smaller size are embedded within the coverage area of larger macro cells, primarily to provide increased capacity in targeted areas of data traffic concentration. Such heterogeneous networks try to exploit the spatial variations in user (and traffic) distribution to efficiently increase the overall capacity of the wireless network.
Based on the cell size, Heterogeneous networks are generally classified according to two major types: Large cells, which include macro cells and macro relays; and Small cells, which include micro cells, pico cells, Home evolved node B (HeNB)/femto cells (usually privately maintained) and small relays. It is a common deployment scenario that macro coverage is overlapped with spotty small cell coverage. Transmission power differences for mobile stations, or User Equipments (UEs) communicating with macro cells and overlapped small cells create significant interference management problems in those HetNets.
In the case of the small cells (pico/femto/HeNB) being located at the edge area of a macro cell, the small cell will experience severe Reverse Link (RL) interference from a nearby UE transmitting (RL) to the macro cell. Similarly, Forward Link (FL) interference from the small cell to the macro cell may be experienced when the small cell is at the edge of the macro cell since the location is far away from the macro eNB and its FL signal is very weak. A characteristic of the HeNB small cells is that access to such cells is normally only open to an authorized small group of UEs. Thus, for a non-authorized UE, no matter how close it is to an HeNB cell, it is unable to handover to the HeNB cell, and accordingly, must continue to maintain communications with the macro cell. When the UE is located sufficiently close to the HeNB that it could handoff to that cell but for the lack of authorization, but located somewhat distantly from the eNB of the macro cell, this will lead to even more severe interference between macro and femto/HeNB cells. Additionally, many of the legacy UEs cannot be re-configured to access an HeNB cell, even if authorization for such access to a given eNB cell were otherwise desired. It is also noted that there are already a large among HeNB cells being deployed within macro cells and the density of such deployments is expected to sharply increase in the future.